A plan to slash 20,000 full-time soldiers and replace them with reservists is six years behind schedule, a study found.

The spending watchdog said it had failed to recruit enough soldiers to replace them.

The National Audit Office said the shortfall in reserves, formerly the Territorial Army, “will put pressure on regular units”.

It warned the cuts will “significantly affect the Army’s ability to achieve its objectives and value for money”. Defence Minister Philip Hammond has been under mounting pressure over the Army 2020 project.

Under the restructuring programme, which will see the Army reduced to its lowest levels since the Napoleonic Wars of the early 1800s, the reservist force must grow from 19,000 to 30,000 by 2018.

NO DEFENCE: Margaret Hodge believed the cuts are leaving a shortage of soldiers [PA]

“The Ministry of Defence focused heavily on cutting costs rather than on recruiting and training ”

Margaret Hodge, chairwoman of the Commons Public Accounts Committee

Margaret Hodge, chairwoman of the Commons Public Accounts Committee, said: “The Ministry of Defence focused heavily on cutting costs rather than on recruiting, training and integrating a substantially increased number of reserves, something the Army is already failing to do.

“The MoD went ahead with plans to reduce the number of regular soldiers and increase the number of reservists without even investigating whether it was possible to do this by that time, or even whether it had 19,000 trained reservists to start with.”

Mr Hammond said he was still “confident” the target of 30,000 part-time soldiers would be hit by 2018.